The construction industry commonly uses single ply membranes to provide a waterproof barrier on flat or low-slope roofs. It is prohibitively expensive and difficult to produce and transport a single membrane that is sized to cover an entire roof surface, thus, a plurality of individual membranes are provided and oriented in an overlapping arrangement. The overlapping portions, or splices, of these individual membranes must be secured together to ensure that the plurality of membranes form a single waterproof surface.
In many cases, flashings are used to seal certain locations of the roofing membranes where the membranes meet, such as corners or walls. One type of flashing used is referred to as a tape flashing, which is a laminate and may include a polymeric layer of thermosetting flashing material (i.e., EPDM) laminated to a layer of vulcanized tape adhesive. The polymeric layer may be provided in an uncured state and then cured by exposure to heat over time after being installed on the roof. Alternatively, the polymeric layer of the tape flashing laminate may be provided in a cured state prior to installation.
The polymeric layer of the flashing laminates are formable when in the uncured state, which facilitates installation of the flashing laminate by allowing it to better conform to the underlying surfaces (e.g. corners). However, these uncured flashing laminates are susceptible to punctures, slits, cuts and impact damage, as well as damage caused by building movement and/or wall movement prior to curing of the polymeric layer. When provided in a cured state, the polymeric layer is more durable and resistant to damage, but is difficult to mold to conform to the underlying surfaces of the roofing assembly.
Flashing laminates are often provided in specific sizes and shapes designed for installation at specific locations or edges of the membrane. For example, flashing laminates may include those intended for installation at an outer corner of vertical walls, at the base of curb surfaces, around penetrations through the roofing system, and at a metal flashing, such as a gravel stop, provided at the edge of the roof surface. Certain areas of these flashing laminates are particularly vulnerable to damage while the flashing is in an uncured state. Specifically, the areas where the flashing laminate transitions from a horizontal surface to a vertical surface are particularly vulnerable. In addition, areas at the outer corners of vertical surfaces can also be vulnerable to damage during installation of the flashing tape.
U.S. Pat. No. 6,291,542 discloses a method and apparatus for selectively curing a sheet of ethylene-propylene diene termonomer (EPDM) material to form a roofing membrane for installation on a roof deck. The method includes the steps of providing a sheet formed of EPDM, the sheet having a field and longitudinal edge areas bordering the field; and then simultaneously shielding at least one edge area of the EPDM sheet and exposing at least the field of the EPDM sheet to radiation to cure at least the field of the EPDM sheet, while retaining at least one uncured edge area. An object of the invention is to facilitate splice seaming between adjacent roofing membranes by providing uncured edge areas of the membrane, thereby eliminating a need for adhesives. This method and apparatus does not contemplate selective curing of portions of flashings at vulnerable areas.
Thus, there is a need for an improved flashing laminate that reduces the risk of damage to the flashing during installation and during the curing period without appreciably affecting the formability of the flashing laminate.